I am with Dave - early voting is a significant contributor. This is part of the “ground game” - it tells the party whose door they need to knock on, or whose ballot one needs to fill out. As those numbers dwindle. The board of elections in turn provides daily updates.
Alberta is right too = where mail in became easier or more prevalent. It has a higher propensity for fraud. It made it easier to skip the early voting and go “help” people fill out their ballot.
Results would be vastly different if election day were held only on the 1st Tuesday after the 1st Monday, and absentee ballots only by legitimate excuse. The convenience and decline in public morality have had negative consequences on the integrity of the election.
The inexorable decline of this country has been driven by this delusional, destructive notion that anyone who can breathe on a mirror has the right to have a say in our government.